Self Diagnostics; Default Or Limp-In Mode - Mitsubishi Eclipse Technical Information Manual

(3) Self Diagnostics

Another feature of the TCM is that it helps the techni-
cian find a problem within a malfunctioning transaxle
or control system. It can do this through self-diagnos-
tics. When something goes wrong with any of the
(4) Diagnostic Trouble Codes
In addition to sensing electrical malfunctions, the
TCM can also detect some hydraulic and mechanical
malfunctions that also produce diagnostic trouble
codes. Each code represents a different malfunction.
In order to read the diagnostic trouble codes, the
technician must hook-up a special diagnostic scan
tool, called a scan tool (MUT-II). It will be hooked

(5) Default or Limp-In Mode

Another feature of the TCM is the ability to protect
the transaxle from potentially hazardous.operation,
when certain problems arise. The TCM constantly
monitors its systems. If it senses a problem, it puts
a diagnostic trouble code in memory and shuts down
the electronic controls. When this happens, it is
referred to as default or limp-in. Not all diagnostic
trouble codes put the transaxle into default or limp-in
mode. Only the codes that indicate a problem that
could potentially cause further transaxle internal
damage or hazardous operation. If the TCM fails
for some reason, the transaxle automatically goes
into default.
When the transaxle goes into the default mode,
it automatically shifts to second gear when in any
forward gear selection and stays there. When the
ignition key is turned "off" and then back "on" again,
the TCM resets itself to operate normally until it
senses the fault and again goes into second gear.
POWER TRAIN
major electronic circuits in the TCM and/or its input
sensor and output device network, a two digit numer-
ic diagnostic trouble code is put into memory.
up to a diagnostic connector, located under the
instrument panel.
To retrieve diagnostic trouble codes, it is necessary
to follow the procedures outlined in the Powertrain
Diagnostic Procedures manual for this transaxle.
The TCM can retain up to seven diagnostic trouble
codes in memory at one time.
No matter what forward gear is selected, the vehicle
stays in second gear. Park, Neutral, Reverse, and
Second gear are the only gears that the transaxle
will operate in when in the limp-in mode. The idea
behind limp-in mode is to prevent the customer from
being stranded and to provide them the ability to
drive in (or limp-in) for service.
As mentioned previously in the "Component Identifi-
cation" section, the TCM has the job of controlling
four solenoids in the solenoid assembly. To do this,
the TCM uses its programming and information from
several sensors. Some of the sensors are wired
directly to the TCM and other sensor signals come
from other electronic components across the CCD
bus. The CCD bus is simply a communication link
between the TCM and other electronic components
on the vehicle. The communication link is made
through two twisted wires.